In general, a brake mounted on a wheel chair is constructed such that a swingable lever is provided on a frame of the wheel chair so that part of the lever is pressed against a wheel to apply brakes. Note that since wheels of a wheel chair are constructed to rotate independently, brakes are designed to be applied to the wheels simultaneously.
Incidentally, when a user attempts to start a wheel chair on a slope while being seated therein, an operation is required of releasing brakes while rotating both wheels. However, both hands of the user are occupied to rotate the both wheels in this state. Therefore, it is extremely difficult to operate the lever to release the brakes in the state.
Even if the user operates the lever with one of the hands while press holding one of the wheels with the other hand, the wheel chair so stopped on the slope tends to turn on the wheel so press held with the one hand as an axis, and this may put the user in a dangerous situation. In addition, when the user is so old that he or she does not have enough physical strength, it is easily conceived that he or she cannot start his or her wheel chair on the slope due to a shortage of physical strength required to press hold the wheels.
In addition, not only when starting the wheel chair on the slope but also when climbing up the slope, an action to keep the wheel chair moving forward needs to be taken quickly within a very limited period of time while the wheel chair is advancing on inertia as a result of the rotation of the wheels by the user. Namely, unless the wheels are operated to rotate quickly and continuously, the wheel chair is forced to move backward. Consequently, it is extremely difficult for older and heavily handicapped people to keep the wheel chair running on the slope.
Then, with a view to attaining safe and easy start and continuous climbing movement of the wheel chair on the slope, improved brake apparatuses are proposed in JP-A-7-227408 and JP-A-11-28231.
In the case of a brake apparatus described in JP-A-7-227408, a brake arm is pressed against a wheel by operating a lever so that a braking portion attached to a distal end of the arm is brought into contact with the wheel so as to generate a braking force. However, there are provided two such braking portions, one braking portion functioning as a normal brake apparatus of a type in which brakes are applied while the wheels rotate forward and backward, the other braking portion functioning as a reverse-rotation preventing brake of a type in which brakes are applied only when the wheels rotate backward. Consequently, by using this apparatus, being prevented from descending the slope, the user can safely start the wheel chair from rest on a slope and keep it climbing the slope without having to release the brakes.
On the other hand, in the case of a brake apparatus described in JP-A-11-28231, a normal brake apparatus and a slop-starting brake apparatus are provided in a parallel fashion; the normal brake apparatus being of a type in which brakes are applied when a wheel chair is moved forward and backward by pressing a brake arm against a wheel through operation of a lever, the slope-starting brake apparatus being of a type in which a one-way roller (a roller designed to rotate smoothly in one direction but not to rotate in an opposite direction) is separably brought into contact with a wheel by operating a slope-staring lever which is provided separately from the normal brake lever so that brakes are automatically applied only when the wheel chair is moved backward when the one-way roller is brought into contact with the wheel, whereby when the wheel chair is started from rest on the slope, the wheel chair is only allowed to move forward by allowing only the one-way roller to be brought into contact with the wheel. Consequently, the safe slop starting and climbing can be attained without paying attention to release of the brakes.
However, in either of the brake apparatuses, since the brake force which enables the safe and easy slope starting and climbing is obtained through the construction in which the special members (the arms and the one-way roller) are brought into direct contact with the wheel, there has been caused a problem that the brake apparatus needs to be enlarged in size and weight as the wheels become larger.
In addition, since the brake force is constructed to be obtained through direct contact with the wheels, friction force between the brake member which contacts the surface of the wheel and the wheel changes due to various factors such as the wet surface of the wheel which would result, for example, when the wheel chair is running in the rain, the degree of wear of the wheel (tire) and the air pressure of the wheel, and this change in friction force calls for a change in brake force, leading to a problem that it is difficult to maintain a stable braking performance.
Additionally, since the brake members are exposed outside, there is also caused a problem that the appearance of the wheel chair itself which is equipped with the brake apparatus is aesthetically damaged.
The invention was made in view of the problems that have been described heretofore, and an object thereof is to provide a brake apparatus which can facilitate slope starting and climbing and which can be reduced in size and weight, and another object of the invention is to provide a brake apparatus which can obtain a stable brake force in every condition including running in the rain.